There are known a battery or pure electric vehicle (EV) which uses one or more electric traction motors and a hybrid electric vehicle (HEV) which combines an internal combustion engine propulsion system with an electric propulsion system. These vehicles derive all their electric power from their large capacity rechargeable battery units for power supply to traction motors and air conditioners for air conditioning in their passenger compartments. In some electric vehicle, an improvement in convenience of driving is made by charging its battery unit during regenerative braking and by restoring the battery unit to an acceptable upper charge level with an external battery charger.
It is known from Patent Document 1 to condition air so that interior temperature and the like within a passenger compartment of an electric vehicle may be comfortable or, in other words, carry out a so-called “preparatory air conditioning” during charge in order to ensure comfortable environment for a user to get in the vehicle and drive after charge. By carrying out such preparatory air conditioning during charge, the amount of power consumed by an air conditioner can be saved during driving, resulting in an appreciable extension of driving range between charges in addition to improved comfort in the passenger compartment. The above-mentioned Patent Document 1 proposes intermittently turning on and off an air conditioner in order to reduce load derived from carrying out the preparatory air conditioning.